[llvm] [RISCV] Cost casts with illegal types that can't be legalized (PR #153030)

[via llvm-commits]

hiraditya wrote:

> > Thanks for fixing it quickly. I wonder if we should split cast.ll into smaller files?
> 
> Potentially, there's quite a few RISC-V configurations we should probably be testing which would result in a lot of check lines. I'm not sure what's the best way to split them up. One file per instruction being tested?


That works. @topperc do you have any suggestions?

https://github.com/llvm/llvm-project/pull/153030